From: Drew McDermott <drew.mcdermott@yale.edu>

Date: Wed, 13 Jun 2001 09:12:12 -0400 (EDT)

Message-Id: <200106131312.f5DDCCg10074@pantheon-po02.its.yale.edu>

To: www-rdf-logic@w3.org

Date: Wed, 13 Jun 2001 09:12:12 -0400 (EDT)

Message-Id: <200106131312.f5DDCCg10074@pantheon-po02.its.yale.edu>

To: www-rdf-logic@w3.org

[Pat Hayes] As far as I know, there is no *mathematical* way to distinguish definitions and assertions. Correct me if I'm wrong, but don't logic textbook mention the case where a definition is simply an equality or if-and-only-if? E.g., you might write (bachelor ?x) <=> (and (male ?x) (not (married ?x))). Now take a theory involving the term "bachelor," and you can easily convert it to a theory that doesn't mention the term anywhere. This two-stage process neatly captures the idea of the definition "not being allowed to be false." By the time you catch a contradiction, the definition is nowhere to be seen. Of course, this won't work for recursive definitions, which may be why people like Russell didn't trust them. My knowledge of the history of logic is a bit shaky at this point. -- Drew McDermottReceived on Wednesday, 13 June 2001 09:12:30 UTC

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